Contact member



Nov.v3, 1970 y c. A. DAMM` ErAL 3,538,488

' CONTACT MEMBER Original Filed April 8, 1968 INVENTORS CARL .DAMM

l bx ALBE c. EICHMANN ILLIAM J.

A T RNE Ys HALPERN um United States Patent Int. Cl. Hon 3/06 U.S. Cl. 339-95 6 Claims ABSTRACT OF THE DISCLOSURE An electrical connector including a iiexible armored.

sheath having an insulated conductor threaded therethrough and electrically connected between a plug unit and a breech cap which is adapted for applying a tiring signal to a pyrotechnic cartridge and which has flanged spring pins formed to function both as ground contacts and as spent cartridge extracting means. A braided sheath encircles the armored sheath and is mechanically connected at one end to the breech cap and at the other end through a turnbuckle-like sheath stretching assembly to the plug unit. The stretching assembly enables the braided sheath to be longitudinally stretched so that it tightly grips the armorer sheath and forms therewith a more rigid conduit.

STATEMENT OF GOVERNMENT INTEREST The invention described |herein may be manufactured and used by or for the Government of the 'United States of America for governmental purposes without the payment of any royalties thereon or therefor.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is a division of application Ser. No. 719,629 tiled Apr. 8, 1968 now U.S. Pat. No. 3,504,592.

BACKGROUND OF THE INVENTION Pyrotechnically actuated bomb racks are frequently rendered inoperable by reason of the electrical failure of a connector which terminates at one end in a breech cap adapted for applying a detonation signal to a pyrotechnic cartridge carried in an ejector assembly. The connector needs to be ilexible and cannot be secured to adjacent structure of the bomb rack because the breech cap must be removed to load cartridges. Flexible connectors are subjected to bufEeting by air turbulence during ight which causes the connector to 'vibrate with consequential weakening and eventual severance of the electrical conduction path.

SUMMARY OF THE INVENTION It is the general purpose of this invention to provide an improved electrical connector which assures that a good electrical conduction path will be maintained and which can be made stiff enough to resist the deleterious eiects of buieting by air turbulence and yet does not interfere with easy disconnection of the breech cap from its associated pyrotechnic ejector assembly. Brieily, this is accomplished by providing a flexible armored sheath through which extends an untensioned length of conductor electrically interconnecting the breech cap and an anchor and plug unit; by providing a stretchable sheath which encases the ilexible armored sheath and is mechanically connected in a linkage between the breech cap and the anchor unit; and by providing adjustable stretching devices, such as a breech cap coupling or an assembly interconnected between an end of the stretchable sheath and the cap or the anchor unit, for longitudinally stretch- 3,538,488 Patented Nov. 3, 1970 ICC ing the encasing sheath and causing it to grip the periphery of the armored sheath and form a more rigid conduit which can withstand intense air turbulence. Additionally, the invention `further contemplates that a good electrical conduction path to the pyrotechnic cartridge be maintained by providing ground contact pins of an improved design. The ends of the tubular pins are obliquely cut to facilitate piercing and gripping the cartridge casing when the breech cap has been coupled in operative position to the associated ejector assembly cartridge chamber and to facilitate extracting the spent cartridge.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 represents a side view partially in cross section of a connector according to the invention;

FIG. 2 represents an enlarged view in longitudinal cross section of a portion of a flexible armored sheath included in the connector of LFIG. 1;

IFIG. 3 represents an enlarged side View of a disengaged ground contact pin included in the connector of FIG. 1;

FIG. 4 represents an end view of the pointed end ofthe pin of FIG. 3; and

KFIG. 5 represents an enlarged cross-sectional view of the pin in piercing engagement 'with a cartridge casing.

DESCRIPTION or THE PREFERRED EMBODIMENT Referring to FIG. l, the connector 10 terminates at one end in a breech cap 11.1 generally of the type described in U.S. patent application Ser. No. 700,603, tiled Jan. 25, 1968, by `Carl A. Damm for Breech Cap for Applying Signals to Explosive Cartridges. The breech cap l11 includes a rotatable, inwardly flanged coupling 12 which is connected to a barrel 1.3 of an ejector assembly (not shown such as that generally described in U.S. Pat. No. 3,036,852 to C. W. IMullison, issued May '29; 1962, and in U.S. Pat. No. 3,431,824 to Carl A. Damm issued Mar. 11, 1969 for Ejector Assembly With Lockable Store- Engaging Presser Foot. The breech cap further includes an apertured breech closing plate 14 through which protrude force lit, flanged ground contact pins 15, hereinafter more fully described, and a spring-loaded primary contact 16. The pins 15 and 16 establish good electrical contact with a pyrotechnic cartridge '17 which is received within the barrel .13 and is of the type detonated by an electrical tiring signal. The tubular coupling 12 may include a plurality of lcey slots (not shown) longitudinally extending from the barrel adjacent end of the coupling 12 and sized to receive a spring loaded key (not shown) for preventing relative rotation of the coupling 12 and the barrel 13.

'Ihe breech cap 11 also includes a flanged, stainless steel pressure dome 18 which is welded to and closed by the plate 14 and which, among other things, sandwiches the ground contact pins 15 in position. The rotatable coupling 12 is retained adjacent the anged end of the dome 18 by a metal snap ring 12a seated in a peripheral groove formed in the dome 18. A llexible, insulated conductor 19 which extends into the dome 18 has a stranded signal lead (not shown) electrically connected at one end with the primary contact 15 and has an inner ensheathing brazed ground 'shield (not shown) insulated from the lead and mechanically and electrically connected to the dome 18. The other end of the conductor 19 extends into a hollow anchor unit 20 and is electrically connected to a plug 21 which protrudes from the anchor unit 20. The anchor unit 20 is rigidly connected as by bolts (not shown) with a framing structure 22 rigidly connected to the bomb rack after insertion of the plug 21 into an aperture 22a formed in the structure 22 for establishing an electrical connection with a recessed receptacle 23 mounted in the aperture 22a. The receptacle 23 is electrically connected with a control unit (not shown) which provides the electrical tiring signal to be applied by the cap 11 to the cartridge 17.

The conductor 19 extends through an aperture formed in the end of the dome 18 remote from the barrel 13 and is threaded through a tubular boss 30 which is lixed to and protrudes from the dome 18. The extended end of `the boss 3() terminates in a radially extending flange 31 and has a coaxial bore 30a extending thereinto which is sized to slidingly receive an end of a llexible armored sheath 32 through which the conductor 19 is threaded. The other end of sheath 32 is slidingly received by a turnbuckle-like stretching assembly 40 through which the conductor 19 is threaded.

The stretching assembly 40 includes a coaxially apertured, internally threaded adjusting bolt 41 which has a hexagonal head and oppositely directed, similarly pitched, external threads and which is threadably engaged by the anchor unit 20. One end of a coaxially apertured fitting 42 is threaded into the bolt 41. The other end of the fitting 42 terminates in a anged boss 43 having a coaxial bore 43a extending thereinto which is sized to slidingly receive the other end of the armored sheath 32. The medial portion of the fitting 42 includes a radially projecting, locking ange 44. The iitting 42, the adjusting bolt 41 and the anchor unit 20 are so interconnected that threading the bolt into the anchor unit 20 causes the fitting 42 and its boss 43 to be drawn toward the anchor unit 20.

It is preferred that the conductor 19 not be tensioned. i

By loosely threading the conductor 19 through the armored sheath 32 and forming a loop or bend 19a therein within the cavity of the anchor unit 20, a connector conn liguration is established wherein little vibration is transmitted to the conductor lead which could eventually cause an electrical failure.

A tubular braided sheath 50 of `stainless steel having a plurality of double-stranded interwoven helical coils 51 is firmly connected at its ends to the bosses 30 and 43 of the cap 11 and the litting 42 of the stretching assembly 40 as by swaged sleeves S2 and 53. While the braided sheath may be joined to the boss 30 of the cap 11 by any desired method, the preferred embodiment includes a thin polyurethane sheath 54 which extends along the periphery of the boss 30 and which provides a seat into which the strands 51 of the braided sheath 50, which have been bent over the ilange 31, may be imbedded by the swaged sleeve 52. Another desirable method (not shown) of swaging the braided sheath 50 to the boss 43 of the stretching assembly 40 contemplates the use of a pair of swaged sleeves made of materials having differing shrink rates so that the inner sleeve made of a material such as plastic is swaged directly to the boss 43 and provides the seat into which the strands 51 may be irnbedded by the overlying swaging sleeve.

The length of the braided sheath 50 relative to the length of the armored sheath 32 is chosen so that in the particular installation the substantially untensioned sheath 50 assumes the greater diametered profile, generally indicated in exaggeration by dotted lines in FIG. l, when the coupling 12 is unthreaded or the assembly 40 is adjusted to have its greatest integral length. For installing the connector in a particular rack, the assembly 40 is adapted for a sufficient initial reduction in length when the cap 11 has been lirmly seated against the cartridge 17 so that the braided sheath 50 can be longitudinally stretched and reduced in diameter so that the helical strands 51 are stretched and tensioned to firmly grip the underlying periphery of the armored sheath 32 and form therewith a conduit of desired rigidity. The boss 43 is long enough so that the end of the armored sheath 32 remains within the bore 43a after the assembly 40 has been shortened to cause the braided sheath 50 to be necked down for tightly gripping the underlying armored sheath 32. Thereby, a substantially rigid conduit may be formed which can withstand the bufleting effects of air turbulence. At any time thereafter, the stiffness of the conduit may be relaxed by loosening the coupling 12 to untension the braided sheath 50. When the breech cap 11 is disconnected from the barrel 13, the armored sheath 32 may be llexed or bent to facilitate extracting the spent cartridge 17 and loading another cartridge 17. Further adjustment of the assembly 40 is usually unnecessary unless the coupling 12 is unable to sufficiently stretch the sheath Sil.

Referring to FIG. 2, the armored sheath 32 is formed from a helically lcoiled strip 61 having an inwardly depending tongue 62 which interlocks with a trough 63 inwardly depending from the confronting edge of the adjacent turn of the strip 61. Since the strands 51 of the braided sheath 50 tightly grip the periphery of the coiled strip 61 when the stretching assembly 40 has been tightened, llexure or bending of the connector 10 is inhibited. Also, when the braided sheath 50 is stretched to radially compress the armored sheath 32, the tongue `62 tends to more closely engage the trough 63 and resist longitudinal sliding movement characteristically present when the armored sheath 32 is bent. The armored sheath 32 also includes a flexible plastic liner 64 which facilitates conductor insertion and protects the conductor 19 from damage by the sheath 32.

Referring again to FIG. l, the head of the adjusting bolt 4l has a plurality of longitudinal slots such as 41a formed therein, any one of which may be longitudinally registered with keying slots 26a and 44a formed in the anchor unit 2li and the locking flange 44 of the fitting 42. An elongated key 70 is held in locking position by a pair of bifurcated spring clips 71 and 72 spaced to be arranged on opposite sides of the head of the bolt 41 for clipping engagement Iof the Shanks of the fitting 42 and the bolt 41. The key 70 is positioned to prevent rotation of the adjusting bolt 41 once the desired degree of longitudinal stretching of the braided sheath 50` has been imposed. A snap-on plastic cover functions to streamline the connector configuration, reducing the causation of turbulence, and to protect the stretching assembly 40 from the accumulation of dirt and ice which could impair its operation.

Referring to FIG. 3, the stainless steel ground contact pins 15 are fabricated from flanged, cylindrical spring pins made of about two tunis of spirally wound rectangles of spring steel. As shown in FIG. 4, the piercing point 91 of the pin 15 has been formed by obliquely truncating a cylindrical pin as by cutting or grinding to form an elliptical pin terminus lying in a plane extending obliquely of the longitudinal axis A of the pin 15. It has been found that, as shown in FIG. 5, when the pin 15 is being forced into the aluminum casing of the cartridge 17 by threading the coupling 12 onto the barrel 13 to seat the plate 14 against the cartridge 17, the laminated walls of the pin point 91 tend to slightly diverge outwardly of the pin axis A and be forced obliquely into the aluminum casing. The furthest projecting portion of the point 91 is deflected outwardly the greatest degree. The above-described pin conliguration not only provides an excellent electrical contact with the cartridge 17 but also facilitates spent cartridge extraction in that, as the uncoupled breech cap 11 is withdrawn `from operative position, the points of the pins 15 tend to continue to grip the cartridge 17 and extract it from the barrel 13.

Several factors influence the design of the pins 15. For example, it has been discovered that the distance that the points of the stainless steel spring pins 15 project beyond the plate 14 should be about eighteen-thousandths vof an inch when three ground contact pins having onesixteenth inch diameters are to pierce an aluminum cartridge casing. Longer point projections prevent complete pin penetration and leave a gap between the plate 14 and the cartridge which can cause the pins 15 to be subjected upon detonation to sufficient cartridge kickback to stress the pins 15 beyond their elastic limits and impair the reuse of the cap 11 and connector 10. It has been found that when the projecting ends of the pins 15 are too blunt, e.g., define a plane substantially normal to the pin axis, the pins will not pierce the aluminum cartridge casing a sufiicient degree for gripping engagement. On the other hand, if the points 91 are too sharp, e.g., in the above specific example, define a plane which is about 30 oblique to the pin axis A, seating the cap 11 on the barrel 13 and tightening the coupling 12 causes the material in the points 91 to be stressed beyond its elastic limit, thereby causing pin point splaying and impairing reuse of the connector i. While 45 points usually have been found to be satisfactory for three one-sixteenth inch diametered pins used to pierce aluminum, a more blunt point such as one defining a plane which is about 60 oblique to the pin axis A is preferred in order to maintain a good electrical conduction path and to assure the feature of ability to extract spent aluminum cartridges. When the spent cartridge 17 is disengaged from the pins 15, the pin points 91 spring back to their normal orientation and are ready for reuse.

Another factor to be considered in designing reusable pins 15 is the peripheral location along the point 91 of kthe projected end of the outer longitudinally extending wound rectangle edge 92. When the end of the edge 92 lies along the furthermost projecting half of the point 91,

the pin point material tends to be stressed beyond its elastic limit upon being forced into a cartridge casing and, consequently, tends to be permanently deformed. Permanent pin point splaying can be avoided -by locating the edge 92 in the other half of the pin 15 which projects the least. Thus, the portion of the point 91 being forced l into the casing which will undergo the greatest defiection from the longitudinal axis generally maintains the crosssectional configuration of an unbroken double-layered elliptical arch during the piercing process. Since the material of the portion being inserted is more uniformly stressed, point deformation within the elastic limits of the material is better assured.

It is preferred that the edge 92 be peripherally located halfway between the longitudinal locations of the greatest and least point projections, i.e., that the length of the edge 92 be equal to the average length of the pin. This configuration facilitates mass production of the pins 15 by enabling the use of a pair of jigs having at one end contiguous, coplanar edges slanted at the desired angle for the points 91 and having a plurality of opposed semicylindrical bores extending normal to the slanted edge for receiving a plurality of unfinished pins 15. The edges 92 of the pins 15 may be easily indexed into alignment with the longitudinal boundaries of the bores in one of the jigs prior to positioning the mating jig. The proper peripheral location of the edge 92 is thereby assured for each pin 15.

The invention provides an electrical connector 10 of greatly improved design which v-astly increases the reliability of the bomb rack in that a good electrical connection between the cartridge 17 and the signal source via the receptacle 23 is continually assured. Vibration incident to in-flight conditions does not tend to cause failure of the electrical interconnection between the cartridge 17 and the signal source in that the ground contact pins 15 engage or grip the cartridge casing with spring-like action and in that the conductor 19 does not tend to vibrate and remains in an untensioned state, preserving the conduction path to the primary and ground contacts 15 and 16. The fiexible armored sheath 32 and the tensioned braided sheath 50 coaet to form a substantially rigid conduit through which the conductor 19 is loosely threaded. The relaxable conduit formed thereby resists buifeting and vibration stimulated by air turbulence which could cause severance of the conductor 19 or other failure of the connector 10.

It is contemplated, of course, that other known plug configurations not shown should be utilized. For example, the plug 32 could be mounted on the end of a conduit rigidly secured to the frame which threadably receives a coupling member connected to the plug 21. It is further contemplated that the connector 10 could include thermal insulation liners extending along the length of the armored sheath 32 for preventing possible melting 'of the shield and lead of the conductor 19 in the presence of rocket blasts.

It should be understood, of course, that the foregoing disclosure relates only to a preferred embodiment of the invention and that numerous modifications or alterations may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A contact means for establishing electrical and mechanical connection with an electrically conductive object comprising:

a plate having an aperture passing through the lower surface of said plate; and

a tubular pin formed from a sheet of resilient electrically conductive material wound upon itself about an axis, said pin having a shank portion and a contact portion, said shank portion being received by said aperture and embedded within said plate, said contact portion protruding from said plate for piercing engagement of the object, said contact portion terminating in an end defining a plane oblique to said axis of said pin, a first point on said oblique plane lying closest to the upper surface of said plate and a second point on said plane lying farthest from said upper surface, saidfirst point being approximately in the same plane as the lower surface of said plate, said second point extending beyond said lower surface.

2. A contact member according to claim 1 wherein: said pin includes an outer longitudinally extending edge of said material which has a length not longer than the average length of said pin.

3. A contact member according to claim 2 wherein: said pin includes an outer longitudinally extending edge of said material which has a length equal to the average length of said pin.

4. A contact member according to claim 1 wherein: said contact portion forms a resilient fiange which defiects outwardly away from said axis and presents a curved longitudinal prole when engaging said object, whereby said object is resiliently gripped in substantially coplanar abutment with said plate.

5. A contact member according to claim 4 wherein:

said aperture further passes through the upper surface of said plate; and

the other end of said pin adjacent said shank portion is ush with the upper surface of said plate.

6. A contact member according to claim 5 wherein: said other end is flared.

FOREIGN PATENTS 1,173,597 10/1958` France.

MARVIN A. CHAMPION, Primary Examiner J. H. MCGLYNN, Assistant Examiner U.S. Cl. X.R. 

